Handling of non-integrity protected reject messages in 5G

Abstract

Methods and apparatus are provided for handling of non-integrity reject message in the 5G system. In one novel aspect, the UE upon receiving the reject message via one access without integrity protection, retries one or more other accesses for one or more times before treating the rejection genuine. In one embodiment, the UE attempts the same 5GMM procedure over another access in the same cell/tracking area (TA). The alternative access including other types of 3GPP access and non-3GPP access. Subsequently, the UE can search the service from another cell/TA or another PLMN. In one embodiment, if the UE receives reject cause invalidating the UE with one access without integrity protection, the UE tries the system a few times before treating the reject genuine by tracking an invalidating counter, which is increased by one each time the rejection is received with a cause value invalidating the UE.

What is claimed is: 
     
       1. A method, comprising:
 transmitting a Registration Request by a user equipment (UE) in a 5G system (5GS) on a first access network with a first public land mobile network (PLMN), wherein the UE can access the 5GS core network (CN) through a plurality of access networks include one or more 3rd Generation Partner Project (3GPP) network and at least one non-3GPP network; 
 receiving a Registration Reject from the 5GS with a cause value indicating a non-integrity protected rejection invalidating the UE; 
 updating one or more corresponding rejection counters based on the first access network and the first PLMN, wherein each rejection counter counts a corresponding registration rejection received without integrity protection; and 
 attempting a new Registration Request based on a registration rule, wherein the registration rule allows the new Registration Request with a selected access network and a selected PLMN upon determining one or more registration conditions are met based on a predefined registration selection criterion, and wherein the selection criterion allows a non-3GPP network being selected; 
 wherein the one or more rejection counters include a retry counter increased by one for each registration request sent by the UE; and 
 wherein the registration condition includes the retry counter is smaller than a preconfigured maximum value of UE retry counter. 
 
     
     
       2. The method of  claim 1 , wherein the registration rule selects a qualified access network following a descending priority order comprising: selecting an available access network in a same cell or a same tracking area (TA) as the first access network, selecting an available access network in a different tracking area (TA) with a same PLMN as the first access network, and selecting an available access network in a different PLMN. 
     
     
       3. The method of  claim 2 , wherein the registration rule selects a qualified access network for the new registration request from in 5GS or evolved packet system (EPS) following a descending priority order comprising: a same access network, a different 3GPP access network, and a non-3GPP access network. 
     
     
       4. The method of  claim 3 , wherein a second access network is qualified if an updated rejection counter for the second access network is smaller than a preconfigured maximum value of registration for the second access network. 
     
     
       5. The method of  claim 1 , wherein the 5GS supports evolved packet system (EPS), and wherein the one or more rejection counters include an invalidate counter that is updated for each registration rejection with a cause value indicating a non-integrity protected rejection invalidating the UE. 
     
     
       6. The method of  claim 5 , wherein the UE only treats a rejection as being genuine until the invalidate counter is greater than or equal to a preconfigured maximum value of invalidate counter. 
     
     
       7. The method of  claim 1 , further comprising:
 subsequently receiving a Registration Accept from the 5GS or evolved packet system (EPS); and 
 reset the one or more rejection counters. 
 
     
     
       8. The method of  claim 1 , wherein the non-3GPP access network is a WLAN network. 
     
     
       9. A user equipment (UE), comprising:
 one or more radio frequency (RF) transceivers that transmits and receives radio signals in one or more corresponding radio networks in a 5G system (5GS); 
 a registration request circuit that transmits a Registration Request on a first access network with a first public land mobile network (PLMN), wherein the UE can access the 5GS core network (CN) through a plurality of access networks include one or more 3rd Generation Partner Project (3GPP) network and at least one non-3GPP network; 
 a registration response circuit that receives a Registration Reject from the 5GS with a cause value indicating a non-integrity protected rejection invalidating the UE; 
 a counter circuit that updates one or more corresponding rejection counters based on the first access network and the first PLMN, wherein each rejection counter counts a corresponding registration rejection received without integrity protection; and 
 a retry circuit that attempts a new Registration Request based on a registration rule, wherein the registration rule allows the new Registration Request with a selected access network and a selected PLMN upon determining one or more registration conditions are met based on a predefined registration selection criterion, and wherein the selection criterion allows a non-3GPP network being selected; 
 wherein the one or more rejection counters include a retry counter increased by one for each registration request sent by the UE; and 
 wherein the registration condition includes the retry counter is smaller than a preconfigured maximum value of UE retry counter. 
 
     
     
       10. The UE of  claim 9 , wherein the registration rule selects a qualified access network following a descending priority order comprising: selecting an available access network in a same cell or a same tracking area (TA) as the first access network, selecting an available access network in a different tracking area (TA) with a same PLMN as the first access network, and selecting an available access network in a different PLMN. 
     
     
       11. The UE of  claim 10 , wherein the registration rule selects a qualified access network for the new registration request from in 5GS or evolved packet system (EPS) following a descending priority order comprising: a same access network, a different 3GPP access network, and a non-3GPP access network. 
     
     
       12. The UE of  claim 11 , wherein a second access network is qualified if an updated rejection counter for the second access network is smaller than a preconfigured maximum value of registration for the second access network. 
     
     
       13. The UE of  claim 9 , wherein the 5GS supports evolved packet system (EPS), and wherein the one or more rejection counters include an invalidate counter that is updated for each registration rejection with a cause value indicating a non-integrity protected rejection invalidating the UE. 
     
     
       14. UE of  claim 13 , wherein the UE only treats a rejection as being genuine until the invalidate counter is greater than or equal to a preconfigured maximum value of invalidate counter. 
     
     
       15. The UE of  claim 9 , wherein registration response circuit subsequently receives a Registration Accept from the 5GS, and the counter circuit resets the one or more rejection counters. 
     
     
       16. The UE of  claim 9 , wherein the non-3GPP access network is a WLAN network.